Syringes typically comprise a tubular body within which a piston head is moved axially by means of a plunger so as to dispense the contents of the space within the body ahead of the piston via a needle which is inserted into or under the skin of a person. Many forms of syringe are known, but they all have these general features and the term syringe will be used hereinafter to denote a dispensing device of this type.
Once a syringe has been used to draw blood from a patient or to administer a medicament or other material to a patient, problems arise in the disposal of the used syringe. Whilst the syringe can be constructed so that it can be disassembled and the individual components cleaned and sterilised for subsequent re-use, this is time consuming and costly. It is therefore the common practice to dispose of the used syringe to waste, for example into a strong plastic container which is disposed of by incineration or burial. However, in handling the used syringe there is the risk that the handler may accidentally jab himself with the exposed end of the needle prior to or during insertion into the disposal container. Furthermore, the syringe is disposed of in an operative condition so that it can be retrieved from the disposal container for unauthorised use, for example to inject drugs or the like.
In order to reduce the risk of accidental jabbing with the used needle, it has been proposed to apply a sheath to the needle. However, this retains the axial length of the syringe and needle, which gives problems in the space the syringe occupies in the disposal container. It has therefore been proposed to break the needle off the syringe, for example using a cutter or the like. However, this leaves a sharp needle stump projecting from the end of the syringe which can snag or stab the skin of a user. In British Specification No 2 314 082 it has been proposed that the needle sheath should be used to break the needle away from the end of the syringe at its mounting so as to render the syringe inoperative by removal of the needle. However, in applying the sheath axially over the exposed needle, the user still runs the risk that he will jab himself with the needle. Furthermore, the syringe is still operative and the needle can be replaced.
It has been proposed in U.S. Pat. No. 4,923,443 to form the plunger with a one use construction so that the plunger can be rendered inoperative once the syringe has been used. Although the syringe is now inoperative, the problems of accidental jabbing with the needle and possible re-use of the needle remain.
The need continues for a simple and effective means for rendering a syringe inoperative and for reducing the risk of accidental damage from the needle.
I have now devised a means by which a syringe can be rendered inoperative at the same time as providing a simple means for disposing of the needle which overcomes the problem of handling and disposing of a sharp object.